Problem: If $x \bigtriangleup y = x(y-3)$ and $x \diamond y = x-5y$, find $(5 \bigtriangleup 6) \diamond 1$.
Answer: First, find $5 \bigtriangleup 6$ $ 5 \bigtriangleup 6 = 5(6-3)$ $ \hphantom{5 \bigtriangleup 6} = 15$ Now, find $15 \diamond 1$ $ 15 \diamond 1 = 15-(5)(1)$ $ \hphantom{15 \diamond 1} = 10$.